Effects of Using Laryngeal High-Speed Videoendoscopy Images Visualizing Partial Views of The Glottis on Measurement Outcomes

Preliminary Findings of Vocal Fold Vibratory Characteristics of Singers Analyzed by Laryngeal High-Speed Videoendoscopy

OBJECTIVES

This study investigates the vocal fold vibratory dynamics of singers, which are postulated to differ from those of normal speakers due to the singers' regular vocal training. The measurement of vocal fold vibration involved the utilization of laryngeal high-speed videoendoscopy (LHSV) and subsequent LHSV-based analysis. The focus of the present study is to characterize and compare the LHSV-based measures derived from the glottal area waveform (GAW), namely fundamental frequency (F0GAW), glottal perturbation (jitterGAW and shimmerGAW), open quotient (OQGAW), and Nyquist plots, between singers and normal speakers across genders.

METHODS

Participants comprised 13 singers from a local cultural and heritage academy and 56 normal speakers from a local university, all were evaluated to have normal voices. Each participant underwent LHSV procedures to capture images of vocal fold vibration, which were subsequently analyzed to generate the LHSV-based measures.

RESULTS

Male singers exhibited lower F0GAW, jitterGAW, shimmerGAW, and OQGAW than female singers. When compared to normal speakers, male singers demonstrated higher F0GAW, and lower jitterGAW and shimmerGAW. No difference in OQGAW was found between male singers and normal speakers. Female singers exhibited lower jitterGAW compared to normal speakers, but no differences were observed in shimmerGAW and OQGAW. The results of Nyquist plots indicated no gender-related associations between types of rim width and among singers. However, for rim pattern, male singers were associated with a higher percentage of clustered rim, suggesting more regular vocal fold vibration, compared to female singers and normal male speakers.

CONCLUSIONS

Singers, particularly male singers, demonstrate distinct and potentially superior vocal fold vibrations compared to normal speakers, likely attributed to their regular vocal training, resulting in refined vocal fold configurations even during speaking. Despite the limited sample of singers, the study offers valuable insights into the vocal fold vibratory behaviors in singers analyzed using LHSV.

Nyquist Plot Parametrization for Quantitative Analysis of Vibration of the Vocal Folds

OBJECTIVES

The Nyquist plot provides a graphical representation of the glottal cycles as elliptical trajectories in a 2D plane. This study proposes a methodology to parameterize the Nyquist plot with application to support the quantitative analysis of voice disorders.

METHODS

We considered high-speed videoendoscopy recordings of 33 functional dysphonia (FD) patients and 33 normophonic controls (NC). Quantitative analysis was performed by computing four shape-based parameters from the Nyquist plot: Variability, Size (Perimeter and Area), and Consistency. Additionally, we performed automatic classification using a linear support vector machine and feature importance analysis by combining the proposed features with state-of-the-art glottal area waveform (GAW) parameters.

RESULTS

We found that the inter-cycle variability was significantly higher in FD patients compared to NC. We achieved a classification accuracy of 83% when the top 30 most important features were used. Furthermore, the proposed Nyquist plot features were ranked in the top 12 most important features.

CONCLUSIONS

The Nyquist plot provides complementary information for subjective and objective assessment of voice disorders. On the one hand, with visual inspection it is possible to observe intra- and inter-glottal cycle irregularities during sustained phonation. On the other hand, shaped-based parameters allow quantifying such irregularities and provide complementary information to state-of-the-art GAW parameters.

Assessment of Vocal Fold Stiffness by Means of High-Speed Videolaryngoscopy with Laryngotopography in Prediction of Early Glottic Malignancy: Preliminary Report

Simple Summary

The method described in our manuscript can help to objectively assess the vibration of each vocal fold using larygotopographic analysis of high-speed videoendoscopy (HSV) recordings. We have developed image processing and analysis procedures to detect vocal fold regions in HSV films and quantitatively analyze their shape and kinematics. We proposed the term Stiffness Asymmetry Index which can provide valuable information on the texture and kinematic properties of individual vocal fold tissues, which can be important in the diagnosis of early glottis cancer. Our study showed that a low value of SAI indicated large, non-vibrating vocal fold areas, characteristic of infiltrative lesions such as invasive carcinoma. This important clinical information can help to assess the depth of vocal fold invasion before direct histologic examination and discriminate benign from malignant lesions.

Abstract

One of the most important challenges in laryngological practice is the early diagnosis of laryngeal cancer. Detection of non-vibrating areas affected by neoplastic lesions of the vocal folds can be crucial in the recognition of early cancerogenous infiltration. Glottal pathologies associated with abnormal vibration patterns of the vocal folds can be detected and quantified using High-speed Videolaryngoscopy (HSV), also in subjects with severe voice disorders, and analyzed with the aid of computer image processing procedures. We present a method that enables the assessment of vocal fold pathologies with the use of HSV. The calculated laryngotopographic (LTG) maps of the vocal folds based on HSV allowed for a detailed characterization of vibration patterns and abnormalities in different regions of the vocal folds. We verified our methods with HSV recordings from 31 subjects with a normophonic voice and benign and malignant vocal fold lesions. We proposed the novel Stiffness Asymmetry Index (SAI) to differentiate between early glottis cancer (SAI = 0.65 ± 0.18) and benign vocal fold masses (SAI = 0.16 ± 0.13). Our results showed that these glottal pathologies might be noninvasively distinguished prior to histopathological examination. However, this needs to be confirmed by further research on larger groups of benign and malignant laryngeal lesions.

Description of the Features and Vibratory Behaviors of the Nyquist Plot Analyzed From Laryngeal High-Speed Videoendoscopy Images

Facilitative playback-based subjective measures offer a more reliable evaluation of the vocal fold vibration than those derived from direct inspection of video playback. One of the measures is a Nyquist plot, which presents the analyzed cycle-to-cycle vibratory information in a graphical form. While the potential is evident, the information of the features of the Nyquist plot, which the evaluation is based on, is still incomplete. The current identified features and their vibratory behaviors may be inadequate to guarantee accurate interpretation of the findings. The present study aims to address this issue by examining the features of the Nyquist plot and their vibratory behaviors. A total of 56 young normophonic speakers, that is, 20 males and 36 females were recruited as the participants. Each of them underwent laryngeal high-speed videoendoscopy to record the images of the vocal fold vibration, which were then analyzed to generate the Nyquist plots. The features were identified by inspecting the properties of the plot points forming the Nyquist plots. For each identified feature, its vibratory behaviors were examined. The results revealed four features: rim contour depicting the longitudinal phase difference; left edge shape signifying the glottal configuration, phase closure, and closed phase duration; rim width and rim pattern visualizing the regularity of glottal areas and the regularity of the intracycle variations, respectively. The findings present a more complete reference of the features and their vibratory behaviors that is pertinent for the Nyquist plot interpretation.